1. Field of the Invention
This invention relates to an improved gas feeder for a sulfonation apparatus.
2. Description of the Prior Art
A preferred sulfonation process comprises flowing a gas containing SO.sub.3 into a reaction tube and simultaneously flowing a liquid sulfonatable organic compound along the inner wall of the reaction tube in the form of a film whereby to effect gas-liquid contact between the SO.sub.3 and the sulfonatable compound. Examples of such sulfonation process are disclosed in Japanese Patent Publication No. 37407/52, Japanese Patent Publication No. 8087/73 and Japanese Patent Application Laid-Open Specification No. 72123/73. These known methods, however, involve the disadvantage that if the gas containing SO.sub.3 is not supplied under proper conditions, the organic compound adheres to the gas feed nozzle or injector and the resulting sulfonated product is colored by excessive contact with the SO.sub.3, thereby reducing the quality of the sulfonated product. Especially in case of the multistage reaction, wherein the SO.sub.3 -containing gas is supplied at two or more stages, as disclosed in Japanese Patent Application Laid-Open Specification No. 72123/73, the risk of coloration of the sulfonated product owing to excessive reaction in the second and subsequent gas feed portions increases.